Effect Of Different Curing Temperatures And Inhibitors On Browning Reaction And Quality Of Flue-cured Tobacco

Shandong main cultivated tobacco varieties were used to study the effects of the ways to controlcuring temperature and inhibitors spraying in regulating enzymatic browning reaction during tobaccocuring process. On one hand, the effects of different curing temperature on enzymatic browning reaction,main chemical components and economic characters were studied through setting8treatments duringyellowing stage and color fixing stage with the upper leaves of Zhongyan100, to detect the relationshipbetween curing temperature and enzymatic browning reaction. On the other hand, through spraying thesodium chlorite, ascorbic acid and calcium nitrate on the fresh tobacco leaves, the best inhibitertreatment, the optimal concentration of inhibitor applications and applic ation time which inhibitedenzymatic browning reaction during tobacco processing were determined, The effects of inhibiters onthe quality of cured tobacco leaves，were also studied, This study provide new ways to regulateenzymatic browning reaction, provide base for regulating the enzymatic browning reaction duringtobacco curing process. The main results were as follows:1Leaves of the step heating yellowing temperature treatment had lower water and PPO activityduring later yellowing stage and early color fixing stage, thus, the enzymatic browning reaction waswell inhibited. Furthermore, the cured leaves had higher sugar content, more suitable sugar nicotineratio and nitrogen nicotine ratio, higher first-class tobacco proportion, average price and economiccharacters due to the tobacco inclusion fully degradation during curing process treated with step heating;The slow heating rate during color fixing stage is good for inhibiting tobacco brown reaction. In earlycolor fixing stage, leaves with the slow heating rate treatment had higher water content and lower PPOactivity. There were almost no PPO activities of leaves of the slow heating rate treatment in middlecolor fixing stage, thus, the probability of enzymatic browning reaction was slim. The slow heating ratetreatment increased total sugar, reduced sugar contents and variegated leaf proportion. The highermuscle yellowing temperature is good for inhibiting tobacco brown reaction, but the greenish proportionwas higher. Leaves treated with51℃as muscle yellowing temperature had lower water contents andPPO activity, thus, the enzymatic browning reaction was well inhibited in color fixing stage, but thefirst-class leaf proportion was lower, in contrast, the cured leaves had higher sugar content, suitablesugar nicotine ratio and nitrogen nicotine ratio.2Sodium chlorite, ascorbic acid and calcium nitrate application on the fresh tobacco leaves couldreduced PPO activity during color fixing stage, thus inhibited enzymatic browning reaction. L-Ascorbicacid could also inhibit enzymatic browning reaction on unripe tobacco leaves, while calcium nitrate alsohad the same function on the unripe tobacco leaves.200mg/L was the suitable concentration forascorbic acid and calcium nitrate spraying, while250mg/L was for sodium chlorite spraying. Calciumnitrate single treating had the best effect on inhibiting enzymatic browning reaction in three treatments,sodium chlorite single treating followed, the ascorbic acid single treating was the worst.100mg/Lascorbic acid+250mg/L sodium chlorite+200mg/L calcium nitrate mixed spraying had the best effecton inhibiting the enzymatic browning reaction of fresh tobacco. 3Sodium chlorite single treatment and100mg/L ascorbic acid+250mg/L sodium chlorite+200mg/L calcium nitrate mix spraying leaves had the best surface quality and internal quality. The color ofcured leaves was deep orange, the oil and gloss better; the content of protein and total phenolics contenthigher, the starch content lower, the aroma quality better, the aftertaste comfortable with lightermiscellaneous gas and lower irritation, the overall quality better than others; and the first-class tobaccoproportion and average price were higher, therefore, the cured leaves had better economic returns; andthe chlorine and calcium contents of cured tobacco leaves were within the appropriate range.